1. Field of the Invention
The present invention relates to a scroll type fluid machine which processes coolant, air or other compressible gas, and in particular to a scroll type fluid machine characterized by the provision of a positioning means for a single unorbiting scroll member which is movable in the direction of a substantially straight line passing through a substantial center of the scroll lap of the unorbiting scroll member but unmovable in a direction substantially orthogonal to the above-mentioned substantially straight line, and which is rotatable, and an unorbiting scroll fixing member, and adapted to appropriately mesh the unorbiting scroll member with an orbiting scroll member so as to aim at ensuring a high degree of energy efficiency.
2. Related Art
Scroll type fluid machines have been widely used as compressors in refrigerators, air-conditioners, and others in various fields. In comparison with other compressors having other configurations, such fluid machines may have preferences such as a high degree of efficiency, a high degree of reliability, stillness and the like, and accordingly, they have been prosperously developed and studied.
Brief explanation will be made of one of the arrangements of these scroll type fluid machines. The basic components of the compression part thereof are a stationary scroll, an orbiting scroll and a frame, the frame being fixed to a closed container, and is also fixed to the stationary scroll with the use of vacant holes in the stationary scroll, fixing thread parts of the frame, and a fixing bolts. The basic components of the stationary scroll are a lap, a mirror plate, a lap bottom, a lap tip and a discharge port, and those of the orbiting scroll are a lap, and a mirror plate, a lap bottom and a lap tip.
The basic components of the drive part of the compressor, for driving the orbiting scroll in order to orbit the latter, are a stator and a rotor in a motor, a crank shaft, an Oldham's ring which is a main component of a mechanism for preventing the orbiting scroll from rotating around its axis, a support member of the crank shaft, for rotatably engaging the frame and the crank shaft with each other, and a support part of the orbiting scroll, for engaging the orbiting scroll and an eccentric pin part of the crankshaft with each other so as to be movable in a thrust direction which is a rotating axis direction and rotatable.
Next, referring to FIG. 10, brief explanation will be made of the compressing operation of the scroll type fluid machine. FIG. 10 shows compression chambers 4a1, 4a2, 4b1, 4b2 which are defined by the lap 2a of the stationary scroll 2 and the lap 3a of the orbiting scroll 3, which are meshed with each other. The compression chambers 4a1, 4a2, 4b1, 4b2 shown in this figure are those during compression stroke, and the compressing operation is carried out in such a way that the orbiting scroll carries out orbiting motion so as to reduce the volumes of the compression chambers. During compressing operation, working fluid is sucked into the compression chamber 4 by way of a suction port 5 and a suction space 15 in association with the orbiting motion of the orbiting scroll 3. The sucked working fluid is discharged by way of a discharge space and a discharge port at the time when the compression chamber reaches a position where it is communicated with a discharge port 2e of the stationary scroll after the volume of the compression chamber is successively decreased as indicated by 4a1, 4a2, 4b1 and 4b2. During the orbiting motion of the stationary scroll 2 and the orbiting scroll 3 which are meshed with each other, there is required sufficient gas-tightness in order to prevent occurrence of leakage of the working fluid between the suction space 15 and the compression chambers 4a1, 4b1, between the compression chambers 4a1, 4a2, 4b1, 4b2, and between the compression chambers 4a2, 4b2 and the discharge port 2e, as far as possible.
Next, brief explanation will be made of an example of a fixing structure between the stationary scroll 2 and the frame 7 with reference to FIG. 11 which is a schematic view illustrating an example of the stationary structure. The purpose of fixing the stationary scroll 2 and the frame 7 with each other is to isolate under pressure a space defined between the frame 7 and the stationary scroll 2 from the discharge space or the suction space in order to carry out appropriate compressing operation. In the example of the fixing structure shown in FIG. 11, the stationary scroll 2 and the frame 7 are fixed together by using a vacant hole 2f in the stationary scroll 2, a fixing thread part 7b in the frame 7 and a fixing bolt 20. In order to isolate the space from the discharge space and the suction space under pressure, as shown in FIG. 10, a plurality of vacant holes 2f in the stationary scroll arranged in a ring-like shape. Further, the diameter of the vacant holes 2f is dimensioned so as to allow the fixing bolts 20 to smoothly be inserted there-through in order to facilitate the assembly of the fluid machine.
An example of the positioning means for the stationary scroll, is disclosed in Japanese Laid-open patent No. H5-332267, and is shown in FIG. 12. In this example, a stationary scroll 100 is composed of a first base plate 100a, a first spiral member 100b, and two reference holes 100c, 100d, and with the use of the two reference holes 100c, 100d, the stationary scroll is positioned so that the phases of the spiral bodies of the stationary scroll 100 and the orbiting scroll are precisely shifted from each other by an angle of 180 deg. In FIG. 12, the reference hole 100d is elongated. However, it is should not be limited to such an elongated hole. The elongated hole can facilitate the assembly even though there would be errors in pitch accuracy between the reference holes while the clearances between the engaging pin and the reference holes can be minimized, and the phase relationship between both scrolls can be precisely set.
The fixing structure between the stationary structure and the frame, as mentioned above offers problems in view of obtaining an appropriate engaging condition between the orbiting scroll and the stationary scroll in order to ensure a high degree of energy efficiency. As shown in FIG. 10, in consideration with the meshing between the orbiting scroll lap 3a and the stationary scroll lap 2a, no gaps are theoretically present between the side surfaces of the laps 2a, 3a at positions where the side surfaces are made into contact with each other, and accordingly, the stationary scroll 2 and the orbiting scroll 3 can be directly meshed with each other. However, since machining tolerances are inevitably present, in fact, in machined components including the stationary scroll 2 and the orbiting scroll 3, small gaps are, in general, defined between the side surfaces of the laps 2a, 3a so as to prevent interference between the orbiting scroll lap 3a and the stationary scroll lap 2a during the assembly of the fluid machine and the orbiting motion thereof. Thus, even with scroll type fluid machines with identical specifications, deviation are inevitably caused among the gaps between the side surfaces of the laps 2a, 3a within the range of machining tolerances.
Further, in the example of the fixing structure between the stationary scroll 2 and the frame 7, shown in FIG. 11, it is frequent that a relatively large gap 21 is defined between the vacant hole 2f in the stationary scroll and the fixing bolt 20 as shown in FIG. 11 in order to enable the fixing bolt 20 to be smoothly inserted through the vacant hole 2f in the stationary scroll. Accordingly, when the stationary scroll 2 is fixed to the frame 7, there would be caused such a risk that the stationary scroll 2 is fixed, being rotated or parallelly shifted from the neutral position thereof by a degree corresponding to the gap 21.
FIG. 13A shows a meshing condition between the stationary scroll 2 and the orbiting scroll 3 in such a case that the stationary scroll 2 is fixed at the neutral position which is a theoretically meshing position, and FIG. 13B shows a meshing condition between the stationary scroll 2 and the orbiting scroll 3 in such a case that the stationary scroll 2 being fixed after being rotated and shifted from the neutral position. Although a gap of several .mu.m or several tenth .mu.m is actually present between the side surfaces of the stationary scroll lap 2a and the orbiting scroll lap 3a, due to machining tolerances, but it is not visible by its size. Referring FIG. 13A, gaps B1, B2 and C1, C2 defined between the stationary scroll lap 2a and the orbiting scroll lap 3a in parts where they make contact with each other, are depicted being exaggerated. The X-axis and Y-axis and the center of the stationary scroll lap 2a are denoted as XF, YF and OF, respectively, and the X-axis and Y-axis and the center of the orbiting scroll lap 3a are denoted as XM, YM and OM, respectively.
FIG. 13A shows a meshing condition in which the orbiting scroll 3 is orbited in the positive Y-axial direction, and the Y axes of the stationary scroll lap 2a and the orbiting scroll lap 3a are coincident with each other. FIG. 13B shows a meshing condition in which the stationary scroll 2 is rotated counterclockwise about the center OF of the stationary scroll lap from the condition shown in FIG. 13A. When the stationary scroll 2 is rotated and then fixed, the parts B1, B2 and C1, C2 shown in FIG. 13A are changed into parts B3, B4 and C3 and C4. The gaps C3 and C4 are decreased while the gaps B3 and B4 are increased. If the stationary scroll is rotated and moved counterclockwise, and is then fixed, as shown in FIG. 13B, the stationary scroll 2 cannot be rotated at an angle by which the gap between C3 and C4 becomes 0. Contrary, if it is rotated clockwise and then fixed, the stationary scroll 2 cannot be rotated at an angle by which the gap between B3 and B4 becomes 0.
FIGS. 14A to 14D show meshing conditions between the stationary scroll 2 which is fixed after the rotation and the movement shown in FIG. 13B, and the orbiting scroll 3 at angular intervals of 90 deg. in the order of FIGS. 14A to 14D, and explanation will be made of varying situations of gaps D1 to D5 and E1 to E5 which are produced in the meshing between the stationary scroll 2 fixed after rotation and movement, and the orbiting scroll 3. The X- and Y-axes and the center of the stationary scroll lap 2a are denoted by XF, YF and OF, respectively, and the X-axis and Y-axis and the center of the orbiting scroll lap 3a are denoted by XM, YM and OM, respectively. The gap D1 corresponding to B3 in FIG. 13B is larger than the gap which is fixed at the neutral position, and is maintained to be large always as shown by D1 to D5 during orbiting. Meanwhile, the gap E1 corresponding to C3 in FIG. 13B is smaller than the gap which is fixed at the neutral position, and is maintained to be always small as shown by E1 to E5 during orbiting. In particular, the possibility of such a tendency that the size of the gap produced through D1 to D5 is greater than that of the gap produced at the neutral position is high since it is defined between the laps having different curvatures caused by rotation and movement. In this case, the compression chamber in which D1 to D5 constitute a seal part, has a gap which becomes large always so that leakage during compression is increased, and accordingly, the energy efficiency of the scroll fluid machine is greatly lowered.
Further, in the fixing method as shown in FIG. 11, the stationary scroll is fixed in such a condition that it is rotated and translated within a range of processing tolerance, the size of the gap corresponding to the seal part of the compressing chamber becomes nonuniform, and as a result, the energy efficiency is largely uneven among scroll type fluid machines even having an identical specification.
Further, a stationary scroll fixing means using two reference holes shown in FIG. 12 and disclosed in the Japanese Laid-Open Patent No. H5-332267 offers several problems in view of ensuring an appropriate meshing condition between the orbiting scroll and the stationary scroll, and high energy efficiency. The positioning means using two reference holes can precisely position the stationary scroll at a preset fixing position. That is, it may be construed that the meshing condition between the stationary scroll and the orbiting scroll has been previously determined. However, since dimensional deviations within processing tolerance are inevitably present among the stationary scroll, the orbiting scroll, the Oldham's ring, the frame and the like, and it can be hardly said that the fixing position of the stationary scroll, which has been previously set, always exhibit an appropriate meshing condition between the stationary scroll and the orbiting scroll. Even though the elongated hole as shown in FIG. 12 is used, the fixing position is still determined directly through the combination with the reference hole 100c, that is, the appropriate position of the fitting pin is not determined in the range of the elongated hole. Thus, although the positioning means disclosed in this well-known example can position the stationary scroll, surely at the preset fixing position of the stationary scroll, it cannot always be said that this fixing position exhibits an appropriate meshing condition between the orbiting scroll and the stationary scroll.